The linear-log converter in its analog form has been extensively used in spectrophotometry for absorbance measurements. In this form advantage is taken of the logarithmic characteristics of the base-emitter junction of a transistor used in the feedback link of an operational amplifier to convert a linear amplifier input into a log output. However, a range of over two decades of input begins to see deviation from the log characteristic.
With modern spectrophotometers using holographic gratings and much reduced stray light a wider log, i.e. absorbance, output is essential. Digital performance of the linear-log conversion is limited by digitation noise in the analog to digital converter.